Background/Purpose: Presence of Minimal Disease Activity (MDA) in Psoriatic Arthritis (PsA) is determined using a patient Visual Analogue Scale (VAS) global PsA activity and VAS pain. Electronic questionnaires for patients to complete at home have great advantages for both patient, researcher and physician, but this implies that physical examination and VAS does not occur simultaneously.  We aim to compare a paper VAS at the clinic and electronic VAS at home in psoriatic arthritis and to assess impact of replacing VAS at the clinic by the at-home questionnaires.  

Methods: Questionnaires collected in the Dutch south-west Early Psoriatic Arthritis CohoRt (DEPAR) were analyzed. Patients filled out the VAS during their appointment and received a link to the online data-base a week in advance. Patients without an email-address received questionnaires by post. The VAS questionnaire contains a VAS global, VAS joints, VAS psoriasis and VAS pain. Data with both visit- and home VAS present within two weeks of each other were used.

The number of patients without a clinically important difference in the two scores were calculated in two ways: difference of <0.5 SD and <10 mm. Impact on determining disease activity was analyzed using MDA (5/7 equals remission, with VAS criteria VAS-Global ≤20 and VAS-Pain ≤15). Reclassification of being in MDA based on VAS-Visit vs. VAS-Home was analyzed.

Results: In total 839 questionnaires of 221 patients were available for analysis (Table 1). The VAS-Home had significantly higher scores than the VAS-visit, with the biggest difference in the VAS-Global (mean difference 4 mm, 95%CI 3-5, P<0.05). No significant differences were observed between the paper (n=86) and electronic (n=753) groups. In 66%, the two VAS-Global measurements were within 0.5 SD and in 60% within 10 mm. Using the VAS-Global remission criteria of MDA (≤20) resulted in 12% low at visit and high at home and the reverse in 8%. Similar percentages are seen in the VAS-Pain assessment. Using different VAS scores in MDA reclassified 87 assessments (10%): in 54 measurements the patient was in MDA when using VAS-Visit but not when using VAS-Home and the reverse in 33.

Conclusion: In 1 out of 3 measurements replacing paper clinic VAS by electronic at home VAS would result in a difference that reaches clinical importance. Patients report higher scores at home than during a clinical visit, resulting in a lower number of patients reaching MDA and a reclassification of 10%.

Table 1. VAS-Scores